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Merger in the early formation stages of our Galaxy

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Computer simulation of the merger between a galaxy like the young Milky Way, whose stars are shown in cyan, and a smaller galaxy, indicated in red.

According to a study based on the second data release of ESA’s Gaia mission, astronomers estimate that a significant merging event like the one shown in this animation has occurred during the Milky Way’s early formation stages, ten billion years ago. Such a merger has led to two important components of our Galaxy, the halo and the thick disc.

Stars belonging to the accreted galaxy, which has been named Gaia-Enceladus, are interspersed with the Milky Way stars and can be seen across the entire sky, but could only be revealed thanks to Gaia’s extraordinary precision.

The simulation shown in this animation is described in papers by Á. Villalobos and A. Helmi published in 2008 and 2009.